Vol 92, No 11 (2018)

An approach to calculating the effects of density fluctuations is generalized with allowance for the movement of molecules in small condensed multicomponent heterogeneous systems (e.g., droplets, microcrystals, and adsorption on microcrystal faces). The collective character of statistical sums of vibrational, rotational, and translational motions of separate molecules in dense phases is expressed in dependences of these statistical sums on the local configurations of neighboring molecules. Using the quasi-chemical approximation with allowance for interparticle interactions reflecting the effects of direct short-range correlations, a relationship is derived between the statistical sum of a system consisting of a multicomponent mixture of molecules and the statistical sums of individual components. A structure is formulated for isotherm equations associating the density of mixture components and their chemical potentials in a thermostat, and for pair distribution functions.

The heat capacity and volumetric properties of cadmium iodide solutions in acetonitrile (AN) are measured at 298.15 K by calorimetric and densimetric means. Standard partial molar heat capacity \(\bar {C}_{{p,2}}^{^\circ }\) and volume \(\bar {V}_{2}^{^\circ }\) of CdI₂ in AN are calculated. Standard heat capacity \(\bar {C}_{{p,i}}^{^\circ }\) and volume \(\bar {V}_{i}^{^\circ }\) of the cadmium ion in AN at 298.15 K are determined. The effect produced by the nature of such solvents as AN, DMF, DMSO, and MP on \(\bar {C}_{{p,i}}^{^\circ }\) and \(\bar {V}_{2}^{^\circ }\) of the cadmium ion is analyzed, and a substantial contribution from the electrostatic component is discovered.

New isobaric vapor-liquid equilibrium data for the binary mixtures of methylcyclopentane + 2‑methylthiophene, cyclohexane + 2-methylthiophene, methylcyclohexane + 2-methylthiophene and ethylcyclohexane + 2-methylthiophene systems were determined by a modified Rose-Williams equilibrium still under the pressure of 90.00 kPa. All the vapor-liquid equilibrium data measurements passed the thermodynamic consistent test by using the Herington method and the Van Ness test, respectively. No azeotropic behavior was observed in the tested four binary systems. Meanwhile, the experimental data were correlated by the Wilson activity coefficient model and also compared with the original UNIFAC and UNIFAC Dortmund predictive models. All results demonstrated that the original UNIFAC model gave better predictions than the UNIFAC Dortmund model.

The oxidative destruction of β-carotene in the presence of highly oxidized forms of µ-carbido-bis[(5,10,15,20-tetraphenyl-21H,23H-porphyrinato)iron(IV)] (1 → 3) or its analog with axially coordinated imidazole (2 → 4) obtained under the action of tert-butyl hydroperoxide ^tBuOOH was studied by spectrophotometry. It was found that compound 3 is the oxo form of compound 1 singly oxidized at the macrocyclic ligand (π radical cation) under the action of which β-carotene is oxidized with a rate constant k = 3.3 L² mol^–2 s^–1. A conclusion is drawn that short-lived compound 4 has unique EAS and is capable of oxidizing ^tBuOOH to form O₂, which makes it possible to consider it the model of peroxidase. The value of k for the reaction with the participation of β-carotene and compound 4 (k = 10.3 L² mol^–2 s^–1) is three times higher than that with the participation of compound 3. If a new portion of β-carotene is added, the process of its oxidative destruction in the presence of compounds 3 or 4 occurs without additives of the dimeric complex and peroxide. A possible nature of compound 4 is discussed, as well as the influence of N-base in the coordination sphere of the complex on the nature of active intermediates and the rate of β-carotene decomposition.

Catalytic properties of solid superacids (WO₃/ZrO₂ and SO₄/ZrO₂), and monolith and H-Beta zeolite-supported phosphotungstic heteropoly acid in gas-phase alkylation of benzene with ethylene to ethylbenzene and in the side reaction of ethylene oligomerization are studied. It was found that H-Beta zeolite had the highest activity and selectivity to ethylbenzene. The use of solid superacid (WO₃/ZrO₂) was shown to be more efficient in low-temperature oligomerization of ethylene.

The clean production requires deep desulfurization to meet stringent environmental specification and aromatics hydrogenation to improve the quality of transport fuels. To achieve this objective, hybrid catalyst was prepared by mixing of PdPt/USY with Ni/ZnO powders. It was found that the hybrid showed higher activity and stability to hydrodesulfurization (HDS) of dibenzothiophene (DBT) and hydrogenation of tetralin than Ni/ZnO or PtPd/USY counterparts. PdPt/USY containing catalysts exhibited high trans/cis ration of decalin, this can be attributed to the isomerization on the acid sites of USY and the reduced interaction between olefinic intermediates with PdPt bimetals. The hybrid catalyst also had high hydrogenation ability and stability to bulky aromatics of pyrene with the existence of DBT. The XRD, XPS, and BET characterizations revealed that PdPt/USY is responsible for DBT HDS, HYD and isomerization whereas Ni/ZnO play supporting role as sulfur adsorbent in hybrid catalyst. Hydrogen spillover between Ni/ZnO and PdPt/USY components facilitates the aromatic hydrogenation and DBT HDS. This study proposed that the PdPt/USY–Ni/ZnO hybrid catalyst may be an alternative in the hydrotreatment of diesel fuel.

The equilibrium concentrations of Zr and Hf in aqueous solutions of HClO₄ {0.8–1.08 mol (kg H₂O)⁻¹}, HCl {0.1–1.05 mol (kg H₂O)⁻¹}, and NaOH {0.24–1.02 mol (kg H₂O)⁻¹} equilibrium with baddeleyite (Zr and Hf)O₂(cr) are determined according to solubility at 250°C and the saturated vapor pressure of the solutions. It is found that hydroxo complexes \({\text{Me}}({\text{OH}})_{3}^{ + }\), \({\text{Me}}({\text{OH}})_{4}^{0}\), \({\text{Me}}({\text{OH}})_{5}^{ - }\), and \({\text{Me}}({\text{OH}})_{6}^{{2 - }}\) are the main products of the hydrolysis of Zr and Hf. In solutions of HCl, the growth in the solubility in comparison with solutions of HClO₄ is due to the formation of hydroxo chloride complexes \({\text{Me}}{{({\text{OH}})}_{{\text{2}}}}{\text{Cl}}_{3}^{ - }\), while for Hf, the reaction proceeds up to the formation of \({\text{HfOHCl}}_{4}^{ - }\). The stability of the complexes of Hf is higher when compared to Zr. This is especially true for neutral complexes \({\text{Me}}({\text{OH}})_{4}^{0}\), the stability of which differs by an order of magnitude, which can lead to the fractionation of these elements in the region of pH from weakly acidic to weakly alkaline. The thermodynamic properties of the complexes of Zr and Hf are determined.

The thermal effects of the interaction between triglycine solutions and Cu(NO₃)₂ solutions at 298.15 K with ionic strength from 0.2 to 1.0 (KNO₃) are measured via direct calorimetry. The enthalpies of CuL⁺, CuHL²⁺, CuHL\(_{2}^{ + }\), CuH₂L\(_{2}^{{2 + }}\) complexation are determined. A complete thermodynamic description of complexation processes is obtained. Based on an analysis of the thermodynamic parameters and the results from spectrophotometric measurements, conclusions are drawn regarding the structure of the investigated complexes.

The reaction between a reduced form of cobalamin (cobalamin(II), Cbl(II)) and periodate in alkaline medium is studied. It is shown that there is no destruction of cobalamin at the ratio of [Cbl(II)] : [IO\(_{4}^{ - }\)] = 2 : 1. The reaction mechanism includes interactions between Cbl(II) and H₄IO\(_{6}^{ - }\) and H₃IO\(_{6}^{{2 - }}\) leading to the formation of aquacobalamin and radicals I(VI), which rapidly oxidize the second molecule of Cbl(II) to aquacobalamin.

The phase diagram of ternary system NaCl−NaBr−H₂O at 348 K was studied by the isothermal equilibrium dissolution method. The solubilities of salts and densities of saturated solutions in the ternary system were determined experimentally. The equilibrium solid phases were also determined by chemical analysis and X-ray powder diffraction. Using the experimental data, the phase diagram of the ternary system was plotted. The diagram comprises one univariant curve and one stationary phase in crystallization filed of Na(Cl,Br).The ternary system was of solid solution type. Density values in the equilibrium solution increase with an increase in the sodium bromide concentration while decrease with an increase of the sodium chloride concentration. Based on the above experimental results, the solid solution compositions can fit well with a quadratic function of the equilibrium liquid composition.

The solubility of 2-chloro-3-(trifluoromethyl)pyridine (CTP) in ethyl acetate, n-butyl alcohol, 2‑propanol, methanol, trichloromethane, acetonitrile, and acetone under atmospheric pressure was measured at 273.15–303.15 K. The solubility of CTP in all eight solvents increased with the increase in temperature. The solubility of CTP had a relation with the polarity of the solvents. The modified Apelblat equation, λh equation, Wilson model, and NRTL model were used to correlate the solubility. The standard dissolution enthalpies were also evaluated.

The presence of directed localized cation–anion interactions in the semihydrate of 2,4,6-triamino-1,3,5-triazine (melamine) dodecahydro-closo-dodecaborate (С₃Н₆N₆Н)₂В₁₂Н₁₂ · 0.5Н₂О is discovered by means of IR and NMR-spectroscopy (¹¹В, ¹Н, С, N). The hypothesis that melamine protonation proceeds on the ring atom of nitrogen is confirmed via quantum-chemical calculations.

The chemical reaction of the 2-[(2,3-dihydroxybenzylidene)amino]benzoic acid (H₃L²) Schiff base ligand with Ru(III), Pt(IV) and Ir(III) transition metal ions form the complexes of formula, [Ru(L)(Cl)₂(NH₃)₂(NH₄)₂] · 2H₂O (1), [Pt(L)(Cl)₃(NH₃)(NH₄)₂] · H₂O (2), and [Ir(L)(Cl)₂(NH₃)₂(NH₄)₂](3), where L is deprotonated ligand at pH 8–9. The carboxylic acid group is deprotonated and forms ammonium carboxylates at alkaline media. The infrared spectra of the complexes show that Schiff base ligand is present as a NO bidentate chelate through –N atom of azomethine and –O atom of OH phenolic groups. These complexes are of non-electrolyte nature. The electronic spectra and magnetic moments data suggest the coordination number. Thermo gravimetric studies show that ruthenium(III) and platinum(IV) complexes containing hydrated water molecules outside the coordination sphere that are presence on their thermal decomposition in the temperature range 50–100°C. Solid powder diffraction XRD patterns of complexes show isomorphism confirming their similar formulation. Scanning electron microscopy (SEM) micrographs of the complexes samples confirm the surface homogeneity. In the transmission electron microscopy (TEM) pictures these complexes are present as a dark spots with particle size of 50 nm.

Molybdenum blue dispersions are synthesized via the reduction of molybdate with glucose in an acidic medium. Spectrophotometry and photon correlation spectroscopy show that, depending on the reducing agent/molybdate ratio and the pH value, both colored complex Mo compounds and dispersed phase particles (large molybdenum oxide clusters) can form. It is shown that particles form in the 1.4–2.2 range of the dispersion medium’s pH and ceases 21 days after synthesis (at room temperature).

Conditions of synthesis are optimized and XRD and thermoanalytical studies are performed for normal maleate [Zn(H₂O)₂(C₄H₂O₄)] and acid maleate [Zn(H₂O)₄(C₄H₃O₄)₂], along with acid Co(II)–Zn(II), Ni(II)–Zn(II) maleates. It is shown that when solid solutions thermally decompose in acidic maleate systems, the kinetically less stable component causes the temperature of decomposition of the more stable component to fall. It is established that the solid residue of Zn(II) maleate after heating to 500°C in a He atmosphere is a composite containing Zn oxide whose reduction to metal begins at 675°C. The decomposition of [(Co_0.1Zn_0.9)(H₂O)₄(С₄H₃O₄)₂] leads to the oozing of metallic cobalt atoms embedded in the channels of the ZnO structure that act as a catalyst for the spontaneous growth of uniform carbon nanotubes on the surface of the composite. After thermal decomposition of the samples in a system of acid Ni(II) maleate–acid Zn(II) maleate, only the bimetallic phase is observed in the composites, and there is no zinc oxide.

Herein, we describe the innovative one-dimensional nanomaterials, electrospun composite nanoribbons (width 10.119 ± 0.186 μm) containing complexes of Eu(TTA)₃(TPPO)₂ and Tb(BA)₃phen in a matrix of polymethylmethacrylate (PMMA). Scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and fluorescence spectroscopy were used to characterize the final products. The novel luminescent composite nanoribbons exhibit green, orange and red fluorescence emission peaks at 490, 545, 592, and 615 nm, which are ascribed to the ⁵D₄ → ⁷F₆ (490 nm) and ⁵D₄ → ⁷F₅ (545 nm) energy transitions of Tb³⁺ ions, and the ⁵D₀ → ⁷F₁ (592 nm), ⁵D₀ → ⁷F₂ (615 nm) transitions of Eu³⁺ ions, respectively. It is observed that the doping percentage and the chosen excitation wavelength could be used to tune the emission color of the samples. The color-tunable luminescent composite nanoribbons have potential applications in the fields of display panels, lasers and bioimaging.

A hydrogel nanocomposite composed of reduced graphene oxide (RGO), iron oxide (Fe₃O₄) nanoparticles, and polyacrylamide (PAM) was prepared using radical polymerization. Different percentages of RGO, Fe₃O₄, and PAM were used to prepare the nanocomposite. Fourier transform infrared spectroscopy (FT-IR) results confirmed the formation of the nanocomposite’s chemical structure. X-ray power diffraction (XRD) patterns revealed the principal peak’s 2θ value to be 77.3° with the size of the nanocomposite particles estimated at 77 nm. Results indicated that the electrochemical capacity of the nanocomposites was controlled by the weight percentage of RGO. Increases to the potential scan rate reduced porosity and surface area, thereby decreasing the electrochemical capacity of the nanocomposites. Moreover, increasing the percentage of Fe₃O₄ nanoparticles in the nanocomposites improved their magnetic characteristics and thermal properties. The latter also improved when the RGO percentage increased.

In this study, the potential of Ge₄₄ and Al₂₂P₂₂ as anode electrodes of Li-ion, Na-ion, and K-ion batteries were investigated via density functional theory. The effect of halogen doping of Ge₄₄ and Al₂₂P₂₂ on ability of metal-ion battery was examined. Obtained results shown that Al₂₂P₂₂ as anode electrode in metal-ion batteries has higher potential than Ge₄₄. Calculated results shown that K-ion battery has higher cell voltage and higher performance than Li-ion and Na-ion batteries. Results display that halogen doping increase the cell voltage and performance of studied metal-ion batteries. Calculated results indicated that F‑doped metal-ion batteries have higher cell voltage and higher performance than Cl- and Br-doped metal-ion batteries. Finally it can be concluded that F-doped Al₂₁P₂₂ as anode electrode in K-ion battery has the highest performance.

Equilibrium curves of the sorption of saponin on activated carbon are analyzed. It is found that the shape of the curve of the sorption isotherm of saponin is determined by processes of association in the solution and sorbent. Based on the calculated parameters, a structure is proposed for an adsorption layer of glycoside on the surface of a carbon-based material, and an assumption about intermolecular dispersion interactions is made.

A polysiloxane with attached groups of rubeanic acid is proposed for the extraction of silver(I), platinum(IV) and palladium(II) from dilute aqueous systems. The sorbent is synthesized for the first time via modern sol–gel technology and has a high degree of surface modification; the concentration of the attached dithiooxamide groups is 0.90 mmol/g. Isotherms of the sorption of silver(I), platinum(IV), and palladium(II) from individual solutions are constructed. The curves are mathematically processed with the Langmuir, Freundlich, Redlich–Peterson, Langmuir–Freundlich, and Toth equations, so exchange capacity values are determined for the modified polysiloxane. The sorbent has good capacitive characteristics and can be used to accumulate large amounts of noble metal ions.

The relationship between the separation capacity and a change in the Gibbs energy of an extraction system with a phase transition of one mixture component is established. A thermodynamic interpretation of the optimum conditions for the separation of mixture components is proposed.

The chromatographic behavior of α, β, and γ-cyclodextrins on three types of reversed-phase chromatography of stationary phases—С4, С8, and С18—is investigated. Patterns of sorption are determined experimentally, and modeling is used to determine the nature of interaction between cyclodextrins and grafted phases. Based on the obtained results and considering experiments on the formation of a complex of β-cyclodextrin and n-hexane, it is suggested that the probability of modifying surfaces of the C4 phase with cyclodextrins in aqueous–acetonitrile mobile phases with low contents (from 5 vol %) of organic modifier is low, and the C18 phase could be used without surface modification of the sorbent when the acetonitrile content is above 10 vol %. To corroborate these conclusions, the constants of complex formation of β-cyclodextrin with some anthocyanins are determined by adding β-cyclodextrin to the mobile phase under the conditions of chromatography on the C4 phase; the same is impossible using the C18 phase.

A solution of MnSO₄ in dimethyl sulfoxide is obtained at a water concentration of 0.2–0.6 M. Most of the water molecules in this solution belong to the hydration shell of [Mn(OH)(H₂O)₅]⁺ · \({\text{HSO}}_{4}^{ - }\)(H₂O)_x ion pairs. The photooxidation of manganese to Mn^III in the presence of an electron acceptor (oxygen or nitro blue tetrazolium) in the solution proceeds when the solution is irradiated with light at the wavelength corresponding to the absorption bands of Mn^II ions. The solution and its photochemical conversions are studied by means of spectroscopy, chemiluminescence, and conductometry. The photolysate is found to contain neither hydrogen peroxide nor free superoxide radical anions. The quantum yield for the photochemical generation of Mn^III is determined for the light absorbed by Mn^II at the ⁶A₁ → ⁴E, ⁴A₁ band: 0.01 ± 0.002 mol/Einstein.

Density functional calculations are performed for boron carbide of the same composition but with different locations of the carbon incorporated into the structure. It is shown that such crystals differ in their unit cell parameters. The data hypothesis confirm that the discrepancy between the unit cell parameters of boron carbide of the same composition is due to the different places where carbon atoms are incorporated into the structure.

The cathodic reduction of nitrate ions in aqueous solutions of sulfuric acid in the presence of chromium(III) ions is studied via potentiometry. It is shown for the first time that nitrate ions are reduced to nitrogen in nitrate-containing solutions in the presence of chromium(III) ions.